Ink composition

ABSTRACT

An ink composition containing an organic solvent and a pigment, which has a little amount of smell, excellent safety and health properties, excellent resin solubility, excellent printing stability and excellent drying properties, causes no corrosion to a printer, and is excellent in adhesion to non-absorbable printing media and good printability, wherein the ink composition comprises as the organic solvent at least one compound selected from compounds of the formulae (1) and (2),  
                 
 
     wherein each of R 1 , R 2  and R 4  independently represents an oxygen atom or —NR 6 — wherein R 6  represents an alkyl group having 1 to 3 carbon atoms, a hydroxyalkyl group, a hydroxyl group or a hydrogen atom, and each of R 3  and R 5  independently represents a branched or non-branched hydrocarbon group represented by CmHn wherein m is an integer of 2 to 8 and n is an integer of 2m-4, 2m-2 or 2m.

FIELD OF THE INVENTION

The present invention relates to an ink composition comprising anorganic solvent and a pigment, which has a little amount of smell,excellent safety and health properties, excellent resin solubility,excellent printing stability and excellent drying properties, causes nocorrosion in a printer, and is excellent in adhesion to non-absorbableprinting media and good printability.

BACKGROUND OF THE INVENTION

Gravure printing for flexible packaging materials, flexographic printingfor sanitary materials, silk screen printing for metal plates, inkjetprinting for indoor and outdoor advertisement, and the like, have beengenerally known as printing methods suitable for non-absorbable printingmedia. However, ink compositions used for these printing methodsgenerally comprise solvents such as toluene, ethyl acetate, methyl ethylketone, methyl isobutyl ketone and cyclohexanone. In this case,obligations such as an ambient concentration setting, the installationof a local exhauster because of smells or the like, and regular medicalexaminations, are imposed. Thus, handling is difficult. Therefore, inkshaving higher safety and health properties are required. In particular,unlike gravure printing, flexographic printing and silk screen printingwhich are performed in exclusive factories, inkjet printing is used inordinary business offices so that it is required to give moreconsideration to safety, hazardousness and odour.

With regard to gravure printing for flexible packaging materials andflexographic printing for sanitary materials, non-toluene inks which donot comprise toluene whose ambient concentration set value is small orwater-based inks which comprise alcohols as a main component, have beendeveloped to improve safety.

On the other hand, in regard to inkjet printing, an ink which uses apolyalkylene glycol solvent or a hydrocarbon solvent (Japanese PatentNo. 3590486) has been developed. However, such inks cannot dissolve thesurface of the printing media, and thus result in poor fixity and waterresistance.

In recent years, accordingly, solvent-containing inks with improvedfixity and water resistance have been developed, by jointly using anitrogen-containing heterocyclic compound such as 2-pyrrolidone orN-methyl-2-pyrrolidone or a lactone compound (JP-A-2005-60716,JP-A-2005-15672, JP-A-2005-200469, Japanese Patent No. 3692365,JP-A-2005-248006) as an assistant solvent. However, due to their strongsolubility, in some cases, these materials and the odour needconsideration.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an ink compositionwhich has a little amount of smell, excellent safety and healthproperties, excellent resin solubility, excellent printing stability andexcellent drying properties, causes no corrosion to a printer, and isexcellent in adhesion to non-absorbable printing media and goodprintability.

The present invention relates to an ink composition containing at leastan organic solvent and a pigment, wherein the organic solvent is atleast one compound selected from the group consisting of a compoundrepresented by the formula (1) and a compound represented by the formula(2),

wherein each of R₁, R₂ and R₄ independently represents an oxygen atom or—NR₆— wherein R₆ represents an alkyl group having 1 to 3 carbon atoms, ahydroxyalkyl group, a hydroxyl group or a hydrogen atom, and R₃ and R₅each independently represent a branched or non-branched hydrocarbongroup represented by CmHn wherein m is an integer of 2 to 8 and n is aninteger of 2m-4, 2m-2 or 2m.

Further, the present invention relates to the ink composition, whichfurther comprises as the organic solvent at least one solvent selectedfrom the group consisting of a solvent represented by the formula (3), asolvent represented by the formula (4), a solvent represented by theformula (5), a solvent represented by the formula (6), a diacetonealcohol solvent, a paraffin solvent, a naphthene solvent and aparaffin/naphthene solvent,R₇CO(OR₈)_(z)OR₉   (3)R₁₀CO(OR₁₁)_(z)OCOR₁₂   (4)R₁₃(OR₁₄)_(z)OR₁₅   (5)R₁₆COOR₁₇   (6)

wherein each of R₈, R₁₁, and R₁₄ independently represents an ethylenegroup or a propylene group, each of R₇, R₉, R₁₀ and R₁₂ independentlyrepresents an alkyl group having 1 to 4 carbon atoms, each of R₁₃ andR₁₅ independently represents a hydrogen atom or an alkyl group having 1to 4 carbon atoms, R₁₆ represents a 2-hydroxyethyl group, R₁₇ representsan alkyl group having 1 to 8 carbon atoms, and Z represents an integerof 1 to 3.

Further, the present invention relates to the ink composition, whichfurther comprises a dispersant.

Further, the present invention relates to the ink composition, whichfurther comprises a resin.

Further, the present invention relates to the ink composition, which isused as an ink for non-absorbable printing media printing.

Further, the present invention relates to the ink composition, whereinthe ink for non-absorbable printing media printing is an inkjet ink.

EFFECT OF THE INVENTION

According to the present invention in which the compound of the formula(1) and/or the compound of the formula (2) is/are added to an ink, thereis provided an ink composition which has a little amount of smell andexcellent safety and health properties, slightly dissolves the surfaceof non-absorbable printing media, on which printing is to be done, andthus remarkably increases the adhesion of the ink without corroding theprinter. Also, due to the increase of resin solubility in the inkcomposition, the shelf life such as viscosity stability, the continuousprinting stability and the ink stability at low temperature areexcellent. Thus, the ink composition offered in this present inventionhas remarkably improved printability.

DETAILED DESCRIPTION OF THE INVENTION

The ink for printing on non-absorbable printing media, provided by thepresent invention, contains a compound represented by the formula (1)and/or a compound represented by the formula (2) as the organiccompound. The content of the compound of the formula (1) and/or thecompound of the formula (2) in the ink is preferably 1 to 50% by weight,more preferably 1 to 20% by weight. When the above content is too small,intended adhesion, ink stability and printability cannot be obtained. Onthe other hand, when it is too large, the ink dissolves the surface ofnon-absorbable printing media too much, which causes roughness on thesurface of printing or a decrease in gloss.

The boiling point, at 1 atmospheric pressure, of each of the compoundsrepresented by the formulae (1) and (2) used in the present invention ispreferably at least 140° C., more preferably 150° C. or more,particularly preferably 160° C. or more. When the boiling point at 1atmospheric pressure is lower than 140° C., drying after printingadvances too promptly and this solvent volatilizes before dissolving thesurface of non-absorbable printing media, so that sufficient adhesioncannot be obtained.

The following Table 1 shows specific examples of the compound of theformula (1). Compound Structual formula 1

2

3

4

5

6

7

8

9

10

11

12

13

14

The following Table 2 shows specific examples of the compound of theformula (2). Compound Structural formula 15

16

17

18

19

20

21

22

23

An organic solvent which is to be used in combination with the abovecompound of the formula (1) and/or the compound of the formula (2) isnot specially limited. For the ink for printing on non-absorbableprinting media, it is preferred to use an organic solvent having aboiling point of at least 140° C. at 1 atmospheric pressure and it ismore preferred to use an organic solvent having a boiling point of atleast 140° C. at 1 atmospheric pressure and a flash point of at least60° C. The mixing ratio of the compound of the formula (1) and/or thecompound of the formula (2) : the organic solvent to be used incombination therewith is preferably 1:0.1 to 84, more preferably 1:1 to29, particularly preferably 1:3 to 21.

The organic solvent used in combination with the compound of the formula(1) and/or the compound of the formula (2) includes solvents representedby the formulae (3) to (6), diacetone alcohol, a paraffin solvent and anaphthene solvent,R₇CO (OR₈)_(z)OR₉   (3)R₁₀CO (OR₁₁)_(z)OCOR₁₂   (4)R₁₃ (OR₁₄)_(z)OR₁₅   (5)R₁₆COOR₁₇   (6)

wherein each of R₈, R₁₁ and R₁₄ independently represents an ethylenegroup or a propylene group, each of R₇, R₉ , R₁₀ and R₁₂ independentlyrepresents an alkyl group having 1 to 4 carbon atoms, each of R₁₃ andR₁₅ independently represents a hydrogen atom or an alkyl group having 1to 4 carbon atoms, R₁₆ represents a 2-hydroxyethyl group, R₁₇ representsan alkyl group having 1 to 8 carbon atoms, and Z represents an integerof 1 to 3.

The solvent of the formula (3) includes glycol mono acetates such asethylene glycol monomethyl ether acetate, ethylene glycol monoethylether acetate, ethylene glycol monobutyl ether acetate, diethyleneglycol monomethyl ether acetate, diethylene glycol monoethyl etheracetate, diethylene glycol monobutyl ether acetate, propylene glycolmonomethyl ether acetate, dipropylene glycol monomethyl ether acetate,ethylene glycol monomethyl ether propionate, ethylene glycol monoethylether propionate, ethylene glycol monobutyl ether propionate, diethyleneglycol monomethyl ether propionate, diethylene glycol monoethyl etherpropionate, diethylene glycol monobutyl ether propionate, propyleneglycol monomethyl ether propionate, dipropylene glycol monomethyl etherpropionate, ethylene glycol monomethyl ether butylate, ethylene glycolmonoethyl ether butylate, ethylene glycol monobutyl ether butylate,diethylene glycol monomethyl ether butylate, diethylene glycol monoethylether butylate, diethylene glycol monobutyl ether butylate, propyleneglycol monomethyl ether butylate and dipropylene glycol monomethyl etherbutylate.

The solvent of the formula (4) includes glycol diacetates such asethylene glycol diacetate, diethylene glycol diacetate, propylene glycoldiacetate, dipropylene glycol diacetate, ethylene glycol acetatepropionate, ethylene glycol acetate butylate, ethylene glycol propionatebutylate, ethylene glycol dipropionate, ethylene glycol dibutylate,diethylene glycol acetate propionate, diethylene glycol acetatebutylate, diethylene glycol propionate butylate, diethylene glycoldipropionate, diethylene glycol dibutylate, propylene glycol acetatepropionate, propylene glycol acetate butylate, propylene glycolpropionate butylate, propylene glycol dipropionate, propylene glycoldibutylate, dipropylene glycol acetate propionate, dipropylene glycolacetate butylate, dipropylene glycol propionate butylate, dipropyleneglycol dipropionate and dipropylene glycol acetate dibutylate.

The solvent of the formula (5) includes glycols such as ethylene glycol,diethylene glycol, triethylene glycol, propylene glycol and dipropyleneglycol and glycol ethers such as ethylene glycol monobutyl ether,propylene glycol monomethyl ether, propylene glycol monobutyl ether,diethylene glycol monoethyl ether, diethylene glycol diethyl ether,diethylene glycol monobutyl ether, diethylene glycol dibutyl ether,diethylene glycol methylethyl ether, dipropylene glycol monomethylether, dipropylene glycol monoethyl ether, dipropylene glycol monobutylether, propylene glycol n-propyl ether, triethylene glycolmonomethylether, triethylene glycol monoethyl ether, triethylene glycol monobutylether and tripropylene glycol monomethyl ether. Diethylene glycoldiethyl ether, diethylene glycol methylethyl ether and dipropyleneglycol monoethyl ether are in particular excellent in view of a littleamount of smell and resin solubility.

The solvent of the formula (6) includes esters such as methyl lactate,ethyl lactate, propyl lactate and butyl lactate.

Specific examples of the paraffin solvent include Isopar G, H, L and M,Norpar 12, 13 and 15, supplied by Exxon, IP solvent 1620 and 2028supplied by Idemitsu Kosan Co., Ltd.; Normal Paraffin SL, L, M and H, Otype Solvent L, M and H, Isosol 300 and 400, Dry Solvent, Dry SolventHigh Soft, Cleansol, Mineral Spirit A, A solvent, and Highalom 2S,supplied by Nippon Oil Corporation; MARUKASOL R supplied by MaruzenPetrochemical Co., Ltd.; Idemitsu Supasol LA25, LA30, LA35, LA41, FP20,FP25, FP30, FP38 and CA25, Diana Fresia P02, P05 and S02, supplied byIdemitsu Kosan Co., Ltd.; Shellsol 71 and 72 supplied by Shell ChemicalsJapan Ltd.; and Moresco White P-40, P-55, P-60, P-70, P-80, P-100,P-120, P-150, P-200, P-230, P-260, P-300 and P-350P, and Moresco Violes,supplied by Matsumura Oil Research Corp.

Specific examples of the naphthene solvent include AF-4, AF-7, AF-5,AF-6, and Teclean N16, N20 and N22, supplied by Nippon Oil Corporation.

Specific examples of the paraffin/naphthene mixed solvent include ExxsolD40, D80, D110 and D130, supplied by Exxon, and Shellsol D100, suppliedby Shell Chemicals Japan Ltd.

The pigment used in the present invention can be selected from variouspigments which are used for printing inks and coatings. Examples of thepigment include, shown as Color Index, Pigment Black7, Pigment Blue 15,15:1, 15:3, 15:4, 15:6 and 60, Pigment Green 7 and 36, Pigment Red 9,48, 49, 52, 53, 57, 97, 122, 149, 168, 177, 178, 179, 206, 207, 209,242, 254 and 255, Pigment Violet 19, 23, 29, 30, 37, 40 and 50, PigmentYellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117,120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168,180 and 185, and Pigment Orange 36, 43, 51, 55, 59, 61, 71 and 74. Withregard to carbon blacks, all carbon blacks such as neutral carbonblacks, acidic carbon blacks and basic carbon blacks can be used. Thecontent of the pigment in the ink is preferably 0.1 to 10% by weight.

In the present invention, it is preferred to incorporate a dispersantfor the purpose of improving the dispersibility of the pigment and thestorage stability of the ink. For example, a hydroxyl group-containingcarboxylic acid ester, a salt of a long-chain polyaminoamide and a highmolecular weight acid ester, a salt of a high molecular weightpolycarboxylic acid, a salt of a long chain polyaminoamide and a polaracid ester, a high molecular weight unsaturated acid ester, a highmolecular weight copolymer, a modified polyurethane, a modifiedpolyacrylate, a polyether ester type anionic surfactant, anaphthalenesulfonic acid formalin condensate salt, an aromatic sulfonicacid formalin condensate salt, a polyoxyethylene alkyl phosphoric acidester, a polyoxyethylene nonylphenyl ether, and stearyl amine acetatecan be used.

Specific examples of the dispersant include “Anti-Terra-U (apolyaminoamide phosphoric acid salt)”, “Anti-Terra-203/204 (a highmolecular weight polycarboxylic acid salt)”, “Disperbyk-101 (apolyaminoamide phosphoric acid salt and an acid ester), 107 (a hydroxylgroup-containing carboxylic acid ester), 110, 111 (a copolymercontaining an acid group), 130 (polyamide), 161, 162, 163, 164, 165,166, 170 (a high molecular weight copolymer)”, “400”, “Bykumen (a highmolecular weight unsaturated acid ester)”, “BYK-P104, P105 (a highmolecular weight unsaturated acid polycarboxylic acid)”, “P104S, 240S (ahigh molecular weight unsaturated acid polycarboxylic acid and a silicontype)” and “Lactimon (a long chain amine, an unsaturated acidpolycarboxylic acid and a silicon)”, supplied by BYK Chemie.

Further, examples of the dispersant include “Efka 44, 46, 47, 48, 49,54, 63, 64, 65, 66, 71, 701, 764, 766” and “Efka Polymer 100 (modifiedpolyacrylate), 150 (aliphatic modified polymer), 400, 401, 402, 403,450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyaninetype)”, supplied by Efka CHEMICALS; “Flowlen TG-710 (urethaneoligomer)”, “Flownon SH-290, SP-1000“and “Polyflow No. 50E, No. 300(acrylic copolymer)”, supplied by Kyoeisha Chemicals Co., Ltd.; and“Disparlon KS-860, 873SN, 874 (high-molecular weight dispersant), #2150(aliphatic polyhydric carboxylic acid) and #7004 (polyether estertype)”, supplied by Kusumoto Chemicals, Ltd.

Furthermore, examples of the dispersant include “Demol RN, N(naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B(aromatic sulfonic acid formalin condensate sodium salt), EP”,“Homogenol L-18 (polycarboxylic acid type polymer)”, “Emulgen 920, 930,931, 935, 950, 985 (polyoxyethylene nonyl phenyl ether)”, “Acetamin 24(coconut amine acetate), 86 (stearylamine acetate)”, supplied by KaoCorp.; “Solsperse 5000 (phthalocyanine ammonium salt type), 13940(polyester amine type), 17000 (fatty acid amine type), 24000”, suppliedby Lubrizol Co.; “Nikkol T106 (polyoxyethylene sorbitan monooleate),MYS-IEX (polyoxyethylene monostearate), Hexagline 4-0 (hexaglyceryltetraoleate)”, supplied by Nikko Chemicals Co., Ltd. and “AJISPER PB821,PB822 (basic dispersant)”, supplied by Ajinomoto Fine-Techno Co.,Inc.The content of the dispersant in the ink is preferably 0.1 to 10% byweight.

In the present invention, a resin is preferably added in order tofurther improve the adhesion to non-absorbable printing media. Examplesof the resin which can be used include an acrylic resin, astyrene-acrylic resin, a styrene-maleic acid resin, a rosin resin, arosin ester resin, an ethylene-vinyl acetate resin, a petroleum resin, acoumarone indene resin, a terpene phenol resin, a phenol resin, anurethane resin, a melamine resin, a urea resin, an epoxy resin, acellulose resin, a vinyl chloride-vinyl acetate resin, a xylene resin,an alkyd resin, an aliphatic hydrocarbon resin, a butyral resin, amaleic acid resin and a fumaric acid resin. Specific examples of theresin include Super Ester 75, Ester gum HP and MALKYD 33, supplied byArakawa Chemical Industries, Ltd., YS Polyster T80, supplied by YasuharaChemical Co., Ltd., Hiretts HRT200X supplied by Mitsui Chemicals,Johncryl 586 supplied by Johnson Polymer Co., Ltd., UCAR solution vinylresin VYHD, VYHH, VMCA, VROH and VYLF-X, supplied by Dow Chemicals, andSolbin resin CL, CNL, C5R, TA5R, supplied by Nisshin chemical IndustryCo., Ltd. The content of the resin in the ink is preferably 0.1 to 10%by weight.

The ink composition of the present invention may contain a variety ofadditives such as a plasticizer, a surface conditioner, an ultravioletlight inhibitor, a photostabilizer, an antioxidant and a hydrolysisinhibitor.

The non-absorbable printing media in the present invention includespolyvinyl chloride sheet, polyolefin sheet, glass and metal. Inparticular, the polyvinyl chloride resin sheet is preferable.

The printing method of the ink composition of the present invention istypically gravure printing, flexographic printing, silk screen printingor inkjet printing. In particular, the inkjet printing is preferable.

The ink composition of the present invention can be produced as follows.First, the pigment is dispersed with the resin or the dispersant in asingle solvent or mixed solvents by means of a paint shaker, a sandmill, a roll mill or a media-less disperser to obtain a pigmentdispersion, and the pigment dispersion is diluted with the solvent ofthe present invention.

EXAMPLES

The present invention will be concretely explained with reference toExamples hereinafter, while the present invention shall not be limitedto these Examples. In Examples, “part” stands for “part by weight”.

First, a pigment dispersion A was prepared in accordance with thefollowing recipe. The dispersion A was prepared by adding a pigment anda dispersant to an organic solvent, stirring the mixture with a highspeed mixer, etc., until the mixture became homogeneous, and dispersingthe thus-obtained mill base with a horizontal sand mill for about 1hour. LIONOL BLUE FG-7400G (supplied by Toyo Ink Mfg., 35.0 parts Co.,Ltd, phthalocyanine pigment) AJISPER PB821 (supplied by AjinomotoFine-Techno 12.5 parts Co., Inc, pigment dispersant) Diethylene glycoldiethyl ether 52.5 parts

Further, a pigment dispersion B was prepared in accordance with thefollowing recipe. The pigment dispersion B was prepared by adding apigment and a dispersant into an organic solvent, stirring the mixturewith a high speed mixer, etc., until the mixture became homogeneous, anddispersing the thus-obtained mill base with a horizontal sand mill forabout 1.5 hours. YELLOW PIGMENT E4GN (supplied by Lanxess, nickel 30.0parts complex azo pigment) Solsperse 17000 (supplied by Lubrizol Co.,pigment 16.5 parts dispersant) Diethylene glycol methyl ethyl ether 53.5parts

Further, a pigment dispersion C was prepared in accordance with thefollowing recipe. The pigment dispersion C was prepared by adding apigment and a dispersant into an organic solvent, stirring the mixturewith a high speed mixer, etc., until the mixture became homogeneous, anddispersing the thus-obtained mill base with a horizontal sand mill forabout 2 hours. Cromophtal Pink PT (supplied by Ciba specialty 32.0 partschemicals, quinacridone pigment) Solsperse 24000 (supplied by LubrizolCo., pigment 12.8 parts dispersant) Ethylene glycol monobutyl etheracetate 55.2 parts

Further, a pigment dispersion D was prepared in accordance with thefollowing recipe. The pigment dispersion D was prepared by adding apigment and a dispersant to an organic solvent, stirring the mixturewith a high speed mixer, etc., until the mixture became homogeneous, anddispersing the thus-obtained mill base with a horizontal sand mill forabout 1 hour. LIONOL BLUE FG-7400G (supplied by Toyo Ink Mfg., 35.0parts Co., Ltd, phthalocyanine pigment) AJISPER PB821 (supplied byAjinomoto Fine-Techno 12.5 parts Co., Inc, pigment dispersant) Compound13 52.5 parts

Example 1

An ink composition was obtained using the pigment dispersion A inaccordance with the following recipe. Pigment dispersion A 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, 4.5 parts vinylchloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Diethylene glycol methyl ethyl ether 78.6 parts Compound7 5.0 parts

Example 2

An ink composition was obtained using the pigment dispersion A inaccordance with the following recipe. Pigment dispersion A 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, vinyl 4.5 partschloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Diethylene glycol methyl ethyl ether 53.6 parts ExxsolD80 (supplied by Exxon) 10.0 parts Compound 7 20.0 parts

Example 3

An ink composition was obtained using the pigment dispersion A inaccordance with the following recipe. Pigment dispersion A 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, vinyl 4.5 partschloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Diethylene glycol diethyl ether 43.6 parts Compound 1340.0 parts

Example 4

An ink composition was obtained using the pigment dispersion B inaccordance with the following recipe. Pigment dispersion B 16.7 partsVinyl resin VYHD (supplied by Dow Chemicals, 3.5 parts vinylchloride-vinyl acetate resin) Diethylene glycol diethyl ether 49.8 partsExxsol D80 (supplied by Exxon) 10.0 parts Compound 13 10.0 parts

Example 5

An ink composition was obtained using the pigment dispersion A inaccordance with the following recipe. Pigment dispersion A 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, vinyl 4.5 partschloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Diethylene glycol dimethyl ethyl ether 13.6 parts ExxsolD80 (supplied by Exxon) 10.0 parts Compound 3 60.0 parts

Example 6

An ink composition was obtained using the pigment dispersion C inaccordance with the following recipe. Pigment dispersion C 12.5 partsVinyl resin VYHD (supplied by Dow Chemicals, 3.5 parts vinylchloride-vinyl acetate resin) Ethylene glycol monobutyl ether acetate44.0 parts Compound 3 40.0 parts

Example 7

An ink composition was obtained using the pigment dispersion B inaccordance with the following recipe. Pigment dispersion B 16.7 partsVinyl resin VYHD (supplied by Dow Chemicals, 3.5 parts vinylchloride-vinyl acetate resin) Diethylene glycol diethyl ether 54.8 partsExxsol D80 (supplied by Exxon) 10.0 parts Compound 20 15.0 parts

Example 8

An ink composition was obtained using the pigment dispersion C inaccordance with the following recipe. Pigment dispersion C 12.5 partsVinyl resin VYHD (supplied by Dow Chemicals, 3.5 parts vinylchloride-vinyl acetate resin) Ethylene glycol monobutyl ether acetate41.0 parts Compound 20 43.0 parts

Example 9

An ink composition was obtained using the pigment dispersion C inaccordance with the following recipe. Pigment dispersion C 12.5 partsVinyl resin VYHD (supplied by Dow Chemicals, 3.5 parts vinylchloride-vinyl acetate resin) Ethylene glycol monobutyl ether acetate79.0 parts Compound 13 5.0 parts

Example 10

An ink composition was obtained using the pigment dispersion A inaccordance with the following recipe. Pigment dispersion A 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, 4.5 parts vinylchloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Diethylene glycol methyl ethyl ether 46.6 partsDiethylene glycol diethyl ether 30.0 parts Compound 13 7.0 parts

Example 11

An ink composition was obtained using the pigment dispersion A inaccordance with the following recipe. Pigment dispersion A 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, 4.5 parts vinylchloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Diethylene glycol dimethyl ethyl ether 3.6 partsCompound 13 10.0 parts Compound 3 70.0 parts

Example 12

An ink composition was obtained using the pigment dispersion D inaccordance with the following recipe. Pigment dispersion D 11.4 partsVinyl resin VYHD (supplied by Dow Chemicals, 4.5 parts vinylchloride-vinyl acetate resin) BYK-361N (supplied by BYK Chemie, acrylicresin) 0.5 part Compound 13 83.6 parts

Comparative Example 1

An ink composition was obtained in the same manner as in Example 1except that the compound 7 used in the recipe of Example 1 was replacedwith diethylene glycol methyl ethyl ether.

Comparative Example 2

An ink composition was obtained in the same manner as in Example 5except that the compound 3 used in the recipe of Example 5 was replacedwith N-methyl-2-pyrrolidone.

Comparative Example 3

An ink composition was obtained in the same manner as in Example 2except that the compound 7 used in the recipe of Example 2 was replacedwith ε-caprolactone

As is evident from the following Table 3, the ink compositions ofExamples 1 to 12, in which the compounds specified in the presentinvention were used as organic solvents respectively, were excellent inall of smell, viscosity stability, printing stability, dryingproperties, corrosion to printer, and adhesion. On the other hand, theink composition of Comparative Example 1 was poor in viscositystability, printing stability, drying properties and adhesion. The inkcomposition of Comparative Example 2was poor in smell, printingstability and corrosion. The ink composition of Comparative Example 3was poor in smell, viscosity stability, printing stability, dryingproperties and corrosion.

The evaluation methods are shown below.

<Smell>

Each of the ink compositions obtained in Examples 1 to 12 andComparative Examples 1 to 3 was independently applied to a polyvinylchloride resin sheet, of which the surface had not been treated, with awire bar No. 6 (supplied by Toyo Seiki sha) in a thermostatic chamber attemperature of 25 ° C. and at a humidity of 30%, and 10 minutes later,the sheets with the ink compositions were sensuously tested for smell. ⊙shows the presence of no unpleasant smell, ◯ shows the presence ofalmost no unpleasant smell, Δ shows the presence of an unpleasant smellto some extent, x shows the presence of an unpleasant smell.

<Viscosity Stability>

The ink compositions obtained in Examples 1 to 12 and ComparativeExamples 1 to 3 were evaluated for viscosity with an E type viscosimeter(supplied by NIKKISO Co., ltd.) before and after a 70° C. and 3-weekaccelerated aging. ◯ shows that the rate of change of the viscosity wasless than 10%, and x shows that the rate of change was at least 10%.

<Printing Stability>

The ink compositions obtained in Examples 1 to 12 and ComparativeExamples 1 to 3 were evaluated as follows. Continuous printing was madeon a polyvinyl chloride resin sheet, of which the surface had not beentreated, with IP-6600 (supplied by Seiko I Infotech, wide format inkjetprinter) at 25° C. The frequency of dot loss, curved flight orscattering of ink was evaluated. ◯ shows that the frequency of dot loss,curved flight or scattering of ink was less than 10 in a 50-hourcontinuous test. Δ shows that the frequency of dot loss, curved flightor scattering of ink was from 10 to less than 20 in a 50-hour continuoustest. x shows that the frequency of dot loss, curved flight orscattering of ink was 20 or more in a 50-hour continuous test.

<Drying Properties>

The ink compositions obtained in Examples 1 to 12 and ComparativeExamples 1 to 3 were evaluated as follows. Solid printing was made on apolyvinyl chloride resin sheet, of which the surface had not beentreated, with IP-6600 (supplied by Seiko I Infotech, wide format inkjetprinter) at 25° C. The period of time required for drying at 40° C. wasmeasured. ◯ shows that the period of time required for drying was within3 minutes. Δ shows that the period of time required for drying was morethan 3 minutes and less than 6 minutes. x shows that the period of timerequired for drying was 6 minutes or more.

<Corrosion to Printer>

A printer material to be brought into contact with an ink was immersedin each of the ink compositions obtained in Examples 1 to 12 andComparative Examples 1 to 3. The change rate of the length of thematerial and the change rate of the weight of the material betweenbefore and after an accelerated aging at 70° C. for 3 weeks wereevaluated. ⊙ shows that one or both of the change rates of the lengthand the weight were less than 3%. ◯ shows that one or both of the changerates were from 3% to less than 6%. A shows that one or both of thechange rates were from 6% to less than 9%. x shows that one or both ofthe change rates were 9% or more.

<Adhesion>

The ink compositions obtained in Examples 1 to 12 and ComparativeExamples 1 to 3 were evaluated for adhesion as follows. Printing wasmade on a polyvinyl chloride resin sheet, of which the surface had notbeen treated, with IP-6600 (supplied by Seiko I Infotech, large-sizedinkjet printer). The printed surface, on which printing had been carriedout, was evaluated for adhesion with a rubbing tester (supplied byTester Sangyo Co., Ltd., type AB301). In the evaluation, a piece ofcloth (Cannequin No. 3) for a test was reciprocated 50 times at a loadof 200 g. ◯ shows that nothing on the printed surface was peeled off. Δshows that partial discoloration occurred. x shows that the basematerial appeared due to peeling off. TABLE 3 Viscosity Printing DryingSmell stability stability properties Corrosion Adhesion Ex. 1 ⊙ ◯ ◯ ◯ ⊙◯ Ex. 2 ⊙ ◯ ◯ ◯ ⊙ ◯ Ex. 3 ◯ ◯ ◯ ◯ ◯ ◯ Ex. 4 ⊙ ◯ ◯ ◯ ⊙ ◯ Ex. 5 ◯ ◯ ◯ Δ ⊙Δ Ex. 6 Δ ◯ ◯ ◯ ⊙ ◯ Ex. 7 ⊙ ◯ ◯ ◯ ⊙ ◯ Ex. 8 Δ ◯ ◯ ◯ ◯ ◯ Ex. 9 Δ ◯ ◯ ◯ ⊙◯ Ex. 10 ⊙ ◯ ◯ ◯ ⊙ ◯ Ex. 11 ⊙ ◯ ◯ ◯ ⊙ ◯ Ex. 12 ◯ ◯ ◯ Δ Δ ◯ CEx. 1 ⊙ X XX ⊙ X CEx. 2 X ◯ X ◯ X ◯ CEx. 3 Δ X Δ Δ X ◯Ex. = Example, CEx. = Comparative Example

1. An ink composition containing an organic solvent and a pigment,wherein the organic solvent is at least one compound selected from thegroup consisting of a compound represented by the formula (1) and acompound represented by the formula (2),

wherein each of R₁, R₂ and R₄ independently represents an oxygen atom or—NR₆— wherein R₆ represents an alkyl group having 1 to 3 carbon atoms, ahydroxyalkyl group, a hydroxyl group or a hydrogen atom, and each of R₃and R₅ independently represents a branched or non-branched hydrocarbongroup represented by CmHn wherein m is an integer of 2 to 8 and n is aninteger of 2m-4, 2m-2 or 2m.
 2. An ink composition according to claim 1,which further comprises as the organic solvent at least one solventselected from the group consisting of a solvent represented by theformula (3), a solvent represented by the formula (4), a solventrepresented by the formula (5), a solvent represented by the formula(6), a diacetone alcohol solvent, a paraffin solvent, a naphthenesolvent and a paraffin/naphthene solvent,R₇CO(OR₈)_(z)OR₉   (3)R₁₀CO(OR₁₁)_(z)OCOR₁₂   (4)R₁₃(OR₁₄)_(z)OR₁₅   (5)R₁₆COOR₁₇   (6) wherein each of R₈, R₁₁ and R₁₄ independently representsan ethylene group or a propylene group, each of R₇, R₉, R₁₀ and R₁₂independently represents an alkyl group having 1 to 4 carbon atoms, eachof R₁₃ and R₁₅ independently represents a hydrogen atom or an alkylgroup having 1 to 4 carbon atoms, R₁₆ represents a 2-hydroxyethyl group,R₁₇ represents an alkyl group having 1 to 8 carbon atoms, and Zrepresents an integer of 1 to
 3. 3. An ink composition according toclaim 1, which further comprises a dispersant.
 4. An ink compositionaccording to claim 1, which further comprises a resin.
 5. An inkcomposition according to claim 1, which is used as an ink for printingon non-absorbable printing media.
 6. An ink composition according toclaim 5, wherein the ink for printing on non-absorbable printing mediais an inkjet ink.